The burden of rheumatic heart disease among children in Lagos: how are we fairing?

Introduction Rheumatic heart disease still remains a cause of morbidity and mortality in low and middle income countries, despite its eradication in developed societies. The study aimed to document the features of children with rheumatic heart disease using clinical evaluation and echocardiography and compare it with reports from other part of the country. Methods A review of a prospectively collected data of patients with rheumatic heart disease who had echocardiography done from April 2007-Dec 2016. Information obtained from patients include age, sex, clinical indication for echocardiography, echocardiographic characterization of the valvular lesions and associated complications. Results A total of 324,676 patients were seen at the Paediatric unit of LASUTH from 2007 to 2016, out of which 36 had Rheumatic heart disease. This translates to a prevalence of 1.1 per 10,000 patients who presented at the study site during the study period. The prevalence of RHD amongst all the patients with structural heart disease was 2.6%. The mean age of patients was 9.12 ± 2.75 years with a male to female ratio of 1.6: 1. The most common valve affected was mitral valve. Heart failure was the most common mode of presentation found in 91.6%. Other complications were pulmonary hypertension and pericardial effusion. Conclusion Rheumatic heart disease is still prevalent among children in Lagos although the prevalence is reducing. Heartfailure is the commonest mode of presentation and complication in them.


Introduction
Rheumatic heart disease (RHD) is a non-suppurative complication of group A Beta hemolytic streptococcal throat infection. It affects children and young adults in developing countries and most of these patients presents in heart failure and require surgical intervention [1]. It is estimated that 12 million people worldwide are affected by rheumatic fever and rheumatic heart disease and two-thirds of these are children between ages of five and fifteen, with 79% of cases from developing countries particularly those in the African continent [2]. Rheumatic heart disease is one of the most common form of acquired cardiovascular disease, in Sub Saharan Africa.
According to a World Health Organization (WHO) estimate over a decade ago, RHD affects children of school going age with a prevalence of 5.7 cases per 1000 school children. 1 The prevalence varies from one region to another but it is known that the rates are still high in sub-Saharan Africa compared with the Western countries [3]. A systematic review conducted in South Africa revealed a high prevalence of RHD, with up to 20.2 per 1,000 children with asymptomatic RHD in some regions in that country [4]. In Nigeria, the prevalence rates varies from region to region with some centres reporting rates of 12.4 per 1,000 children seen in the hospital [5].
The new clinical criteria of 2012 for the diagnosis of ARF/RHD classified ARF into definite initial episode of ARF, definite recurrent episode of ARF in a patient with known past ARF or RHD and probable ARF (first episode or recurrence) [6]. Proven preventive strategies including the use of prophylaxis for rheumatic fever and socio-economic improvement was recognized over thirty years ago [7]. However, in developing countries, social determinants of the disease such as adequate housing, access to primary health care, education and availability of cardiologic diagnostic tools and cardiac surgery are still a major challenge [8]. The decline in the prevalence of rheumatic heart disease in developed countries has been attributed to high standard of living and access to medical care [8].
There is no doubt that rheumatic heart disease still remains a cause of morbidity and mortality in low and middle income countries, despite its eradication in developed societies. This study presents the distribution or rheumatic valvular lesions as seen at echocardiography in the Paediatric cardiology unit of the Lagos State University Teaching Hospital (LASUTH) over a ten period (from January 2007 to December 2016).

Case definition of RHD and pulmonary artery hypertension:
Rheumatic heart disease was defined by the presence of any definite evidence of valve regurgitation or stenosis seen in two planes on Doppler examination and at least two morphologic abnormalities such as restricted leaflet mobility, focal or generalized valvular thickening and abnormal sub-valvular thickening of the affected valves [9]. Pulmonary artery hypertension (PAH) was identified using a combination of ECG and transthoracic echocardiography (Two-dimensional and Doppler) [10]. ECG findings include evidence of right ventricular dilatation and hypertrophy. Two-dimensional features include; increased thickness of the right ventricle, paradoxical bulging of the septum into the left ventricle during systole, right ventricular dilation, right atrial dilatation and or tricuspid regurgitation. Doppler echocardiography was used to measure the pulmonary artery pressure by means of tricuspid regurgitation velocity measurements. Pulmonary pressure greater than 25mmHg at rest is diagnostic of PAH [11]. The severity of PAH is classified as mild (PAH from 25-40mmHg), moderate (PAH from 41 to 55mmHg) and severe (PAH > 55mmHg) [12]. Cardiac catheterization is not routinely done on all patients and thus diagnosis of PAH was not made with cardiac catheterization.  Table 3.
Pre-echocardiographic diagnosis and complications: All the patients were referred from both within and outside the hospital.
The reason for referral and cardiac evaluation are depicted in Figure   1.

Discussion
Rheumatic heart disease is one of the most common and preventable acquired heart disease with valvular heart damage as the hallmark [5].  [20]. The values are lower in the present study compared to those reported in other African studies because of the regional differences in the pattern of RHD in countries in Africa.
Despite the relatively lower values documented in the present study, rates of RHD are known to be high in Africa.
According to a WHO report, Africa is one of the regions with the highest prevalence of RHD and the rate doesn't appear to be decreasing compared to regions like the European countries where it is almost extinct [3]. The reasons adduced for the higher rates includes the availability of major advances in medical and surgical treatment with improved survival and that RHD is more rigorously sort out by echocardiography. Given the lower prevalence of RHD in Southern Nigeria compared to the north, it is imperative that health policies and practices be scaled up in the northern part of the country to reduce the burden therein. The mean age at diagnosis in the present study, is consistent with reports from other studies [5,13,16,20,21]. Most of the children with RHD were over 5 years of age and majority were between 5-10years of age. It has been shown that RHD is more common in children between 5-15years. In the present study, there were more males than the females with

RHD. The finding in this regard is in contrast with most reports
where there is a female predominance in both adult and children [5,13,16,22,23]. However, few studies have reported a male predominance [16,24,25]. The reason for the female predilection in most of the studies is not known. Given that most of the studies are hospital based, not all the patients with the disease are captured. A community based study will present data that will be more representative of the demographics of RHD. In the present study, Mitral regurgitation was the most common valvular lesion occurring either alone or in combination with other valvular lesions. This finding mirrors reports from previous studies [5,13,19]. It has been shown from previous reports that mitral valvular disorders are more common compared to the other valvular lesions. However, the reason for the overwhelming predisposition of mitral valve is yet to be unraveled [26]. Tricuspid regurgitation was second most common valvular lesion seen. It was documented in half of the patients. This finding is not out of place because pulmonary artery hypertension (PAH) is a common complication of RHD and severe forms of PAH will result in tricuspid regurgitation [19,27]. In contracts to the regurgitant lesions, stenotic valvular lesions were only seen in two patients. One patient had a mitral stenosis and another with aortic stenosis. The finding in this regard is not out of place given that stenotic valvular lesions depicts advanced or chronic RHD which is not seen until late adolescents and adulthood.
Rheumatic heart disease is a major cause of morbidity and mortality in affected children. Heart failure and pulmonary artery hypertension were the most common complications observed in the patients. This finding is in keeping with reports from a previous studies [19,22,27].
Heart failure results from valvular insufficiency or stenosis. Given that majority of the patients had mitral insufficiency, it was not surprising that heart failure was a common morbidity amongst them. Similarly, PAH results from severe mitral valvular lesions [19,28]. The finding of pulmonary hypertension in half of the patients is thus in keeping with the prevalent valvular lesions amongst them. The implication of this is that common comorbidities such as heart failure and PAH should be anticipated and managed promptly in all patients with RHD. In a review of predictors of mortality in chronic rheumatic heart disease, Talwar and Gupta [29] noted that, the severity of valvular damage and it's haemodynamic consequences to which PAH and heart failure belongs, is a major factor attributable to mortality in RHD. Other morbidities such as arrhythmia and infective endocarditis are consequence of severe valvular disease that have been associated Page number not for citation purposes 5 in the mortality of patients with RHD, but those were not documented in our subjects. Rheumatic heart disease is a major public health problem in Nigeria and most developing countries. This is because these countries are still burdened with poverty, low level of awareness, poor health seeking behaviour and inadequate treatment. These factors result in persistence of the disease and a poorer outcome [25]. The huge strides achieved in the developed regions of the world in diagnostic options, surgical and interventional management of heart disease has not been replicated in Africa [30]. The diagnostic challenge has reduced in a few centers due to the availability of echocardiography imaging facilities, but this has not been matched with the availability of cardiac surgeries.
It has been recommended that primary and secondary prevention of rheumatic fever should be strengthened at all levels of care [31,32]. This includes prompt use of penicillin prophylaxis in the vulnerable age group, as well as early treatment of streptococcal sore throat which precludes the development of Rheumatic fever and Rheumatic Heart Disease. In addition, long term treatment of rheumatic fever can halt the disease progression [25]. Furthermore, emphasis should be placed on programs such as early case finding and prompt diagnosis of children with rheumatic heart disease, provision of adequate medical services of high quality in hospitals and a good follow up care [8].

Conclusion
In conclusion, there has been a decline in the prevalence of Rheumatic heart disease among children in Lagos in the last decade. Males were more commonly affected than females. Heart failure and pulmonary hypertension were the commonest complications and Mitral valves are the most commonly affected valve.
What is known about this topic  Rheumatic heart disease is an important cause of morbidity and mortality among children in the African Sub region;  It is almost non-existent in the developed countries since the advent of penicillin;  Study done in a populous city is likely to be more representative of the pattern in the developing world.

What this study adds
 Rheumatic heart disease is still prevalent among children in Lagos;  The prevalence of rheumatic heart disease among children in the southern part of Nigeria is lower than those from the northern part of Nigeria;  The prevalence of rheumatic heart disease among children in the southern part of Nigeria is reducing.

Competing interests
The authors declare no conflicts of interest.

Authors' contributions
Barakat Adeola Animasahun was the project leader, she also

Acknowledgments
We gratefully acknowledge the subjects who participated in this study, their parents and caregivers including other staff who were involved in their care.